In the field of pressurized gas storage, particularly for storing in bottles or cylinders of some gases used in the medical field such as oxygen, it is common to provide a residual pressure function on the valves disposed on the bottles. It is basically a check-valve type device with a valve or shutter subjected to a closure elastic force and configured to open when the pressure in the bottle exceeds a rather low given value of the order of few bars. The purpose of this device is to prevent from putting the bottle in direct connection with air when empty. Indeed, in the absence of such a device, when the bottle is empty and the valve is left open, the ambient air of the bottle can come into contact with the inside of the bottle and thus potentially contaminate it. In addition, by connecting the valve outlet to a source of pressurized gas, it may also be possible to at least partially refill the bottle with a potentially contaminating gas. The above mentioned device allows a connection between the inside and the outside of the bottle only when in the presence of a service flow rate, which in practice prevents contamination against the service flow. It also prevents unauthorized forced refilling.
The patent document GB 2349200 A discloses a pressure-reducing valve for a bottle of pressurized gas, with a residual pressure function. The valve essentially comprises a body with a connector to be screwed on a bottle neck, an outlet and a passage connecting the inlet to the outlet. The valve also includes a refilling adapter with a check-valve in connection with the passage. It also includes a shut-off valve in the passage downstream of the branch with the refilling connection, and a pressure reducer disposed downstream of the shut-off valve. It also includes a flow rate selector in the form of a disk with calibrated holes, rotatably driven by a hand-wheel distinct from the hand-wheel of the closing valve. The residual pressure function is integrated in the pressure reducer. This latter includes a shutter mechanically connected to a mobile piston defining with the body a control chamber. The gas under pressure upstream of the shutter flows through a restricted passage and is expanded when passing the shutter in an intermediate position. It then flows through the piston to fill the control chamber defined by the upper face of the piston. If the gas pressure is too high, the resultant force on the piston will move it downwards so as to reduce the flow section of the shutter and vice versa. The upper face of the piston also comprises a concentric ring passage for the gas, this seal being intended to sealingly cooperate with a seat on a portion of the body opposite to the piston. The latter is subjected to an elastic force of a spring which tends to bring the seal in question closer to the seat and to open the shutter. In state of rest, the shutter is opened, which allows the passage of gas through the regulator to the seal in sealing contact with the seat. The hydraulic surface of the piston at the level of the seal in question is slightly greater than the opposite hydraulic surface on the side of the shutter. These two surfaces being subjected to the same pressure, the positive difference of surface between the upper face and the lower face of the piston generates a force directed downwards by lowering the piston and opening the passage between the seal and the seat. These thus form an integrated residual pressure valve in the regulator. The valve of this teaching is therefore particularly interesting from the standpoint of integration of the residual pressure function. However, it is a quite complex and bulky structure particularly because of the presence of the side closure valve.
Patent document U.S. Pat. No. 7,814,931 B2 discloses a flow control device for a fluid, particularly liquid, in particular for sprayers. This device is working at much lower pressures than in the above discussed teachings. The device comprises a body with a first element movable in translation and connected to the body via a sealed membrane. The first movable element is subjected to an elastic force tending to move towards a first seat formed in the body. The membrane is specifically designed to work with this seat. In the rest position, the spring holds the membrane in contact with the circular seat. The fluid passage through the first seat and is sealed by the membrane. The device further comprises a second movable member mechanically connected to the first one and cooperating with a second seat upstream of the first seat. The second movable member has the effect of modulating the fluid passage section upstream of the first seat and the first movable member. When it is decided to open the device, part of the elastic force tending to press the first movable member towards his seat is released. The fluid pressure at the inlet of the device applied to the membrane may move the first member and open the passage. If the pressure and therefore the flow weaken, the passage will be reduced in order to maintain pressure. If the pressure is weakening too much, the passage will automatically close, preventing from having a flow with a low flow rate. This teaching shows an interesting principle that a mobile element flow regulator can provide, namely the closure of the passage at a too low flow rate. However, it does not provide a secure closure of the passage as a significant input pressure is likely to move the first element and open the passage.